The present invention relates to a hydraulic apparatus for remotely shifting a motor vehicle automatic transmission.
Motor vehicle automatic transmissions are provided with a manual control for selecting the mode of operation of the transmission, for example for shifting from park and/or neutral to reverse or to forward drive, or to prevent automatic shifting from a high gear ratio to a lower gear ratio or to straight-through drive, or to overdrive. The manual control or selector takes the form of a steering column mounted pivotable lever, or of a floor mounted lever or quandrant.
The shift control lever or selector conventionally operates, through cables or rods and links, a mode selection arm pivotally mounted on the transmission casing, the mode selection arm being mounted on the end of a control input shaft projecting within the transmission casing and adapted to operate diverse control members within the transmission casing, such as hydraulic valves or solenoids, for functionally establishing an operative mode of the transmission, under the control of the shift control or selector lever. The selected operative mode corresponds to an appropriate position of the shift control or selector lever, and an indication of the selected operative mode is provided to the motor vehicle operator in the form of a visual display, for example in the form of a sector with appropriate markings, each corresponding to a selected operative mode. The visual display or indicator is conventionally placed on one or both edges of a housing mounted on the floor and through which projects the floor mounted shift control or selector lever or, in installations providing a steering column mounted selector lever, the selected mode of operation of the transmission is indicated through the displacement of a cursor in the front of the indicator panel or sector.
Mechanical linkages between the shift control or selector lever and the control input arm of the transmission are rather complex, more particularly in installations wherein it is desired to control the automatic transmission associated with a front wheel drive motor vehicle in which the transmission and differential are enclosed in a common casing, the whole mechanism forming a so-called transaxle which is generally mounted on the motor vehicle frame in front of the engine or parallel to a transversely mounted engine, in view of the many bends required around diverse components installed in a very crowded engine compartment, or in rear-engine vehicles such as buses and coaches.